The present invention relates to curable and cured heat resistant resin compositions comprising
(1) unsaturated polyester resins or unsaturated polyesteramides terminally esterified with a norbornene type group,
(2) an ethylenically unsaturated compound, and,
(3) dicyclopentadiene bis or tris ester of a unsaturated di or tri carboxylic acid.
It is known from U.S. Pat. No. 3,347,806 dated Oct. 17, 1967, that unsaturated polyester resins can be prepared wherein the resins are modified with dicyclopentadiene. However, due to the nature of the disclosed process the polyester resins so prepared have poor mechanical properties, reactivity, and corrosion resistance due to the fact that the resins contain substantial amounts (5 or more percent) of dicyclopentadiene moieties with ether linkages, rather than the more desired ester linkages, as well as Diels-Alder addition products such as endomethylenetetrahydrophthalyl groups.
More recently, in U.S. Pat. No. 4,148,765 (4-10-79) and U.S. Pat. No. 4,233,432 (11-11-80), unsaturated polyesters have been prepared wherein substantially all polyester chains are terminated with a dicyclopentadiene ester moiety. The polyester resins so prepared have improved mechanical properties, reactivity, corrosion resistance, and better economics than the corresponding dicyclopentadiene modified unsaturated polyesters wherein mixtures of dicyclopentadiene etherified and esterified functionality and Diels-Alder addition products are present.
Dicyclopentadiene modified unsaturated polyester compositions containing a vinyl aromatic monomer and a dicyclopentadiene alkenoate having a fast cure time and minimal loss of monomer during curing are disclosed in U.S. Pat. No. 4,167,542 dated 9-11-79. However, said dicyclopentadiene alkenoate is generally a poor solvent for the dicyclopentadiene modified unsaturated polyester alkyd thus high concentrations are required. Furthermore, the corrosion resistance to various aqueous media and solvents as well as the resistance to heat aging are both generally reduced in said polyester compositions.
Although all of those materials have been useful in making products acceptable in the marketplace, there is room for considerable improvement in many of their properties.